Winter’s here! The snow is flying and the days are shorter (don’t forget to turn your clock back!). This means skiing, snowshoeing, tobogganing and other winter sports. But nomatter how much fresh air you get, research shows that the body loses its ability to produce vitamin D from sunlight exposure in the winter. This applies to all of us who live north of the 35th parallel (1). This is of particular concern given vitamin D is present in very few foods AND low levels of vitamin D have been associated with a myriad of diseases including: diabetes, multiple sclerosis, and cancer. Indeed the Canadian Cancer Society recommends a supplement of 1000 IU/day. Researchers have now linked low levels of vitamin D to another group of diseases, the inflammatory bowel diseases.
Inflammatory bowel diseases refer to a group of diseases including Ulcerative Colitis and Crohn’s disease with symptoms such as: stomach cramps, diarrhea, nausea, and vomiting. Interestingly, those living at a northern latitude are much more likely to be affected (2) . In fact, Canada has some of the highest rates in the world with an estimated 201 000 people living with IBD (2008 report).
There are many dietary and environmental factors that could contribute to the increased rates; however, given the link to geographical location vitamin D is a strong contender. In support of this hypothesis, those with Crohn’s disease also have lower blood levels of vitamin D; whether this is a cause, effect or a combination of the two is still uncertain (3). With this in mind a group of investigators set out to see if vitamin D could actually improve the symptoms of inflammatory bowel diseases. The group presented their results at the Annual Meeting of The American College of Gastroenterology and the Globe and Mail reported on their findings. They found that doses of 1000 IU/d had no effect on symptoms, however, a second group that was given a very high dose of 10 000 IU/d showed improvements after 26 weeks.
Although the abstract was reviewed and the results reported in a National newspaper, we want to caution anyone with IBD from using high doses of vitamin D. Much more needs to be done to confirm these results and to fully understand the effects of vitamin D on health. Before any hasty judgments are made, we should be sure to follow the authors closely to see if they publish the full results in a peer reviewed scientific journal and if others support their findings.
Disclaimer: The recommendations for vitamin D intakes were increased by the Institute of Medicine last year to 600 IU/d for adults with an upper limit not to be exceeded of 4000 IU/d. We do NOT recommend that you exceed the upper limit of 4 000 IU/d. If you are considering taking a therapeutic dose of vitamin D (above the upper limit of 4 000 IU/d) for any reason it is important that you do so under the guidance of a physician or health care provider.
(1) Holick MF, Chen TC, Lu Z, Sauter E. Vitamin D and skin physiology: a D-lightful story. J Bone Miner Res 2007 Dec;22 Suppl 2:V28-33.
(2) Raman M, Milestone AN, Walters JR, Hart AL, Ghosh S. Vitamin D and gastrointestinal diseases: inflammatory bowel disease and colorectal cancer. Therap Adv Gastroenterol 2011 Jan;4(1):49-62.
(3) Joseph AJ, George B, Pulimood AB, Seshadri MS, Chacko A. 25 (OH) vitamin D level in Crohn’s disease: association with sun exposure & disease activity. Indian J Med Res 2009 Aug;130(2):133-137.